Overview of Changes

This section is only relevant to people who are familiar with the details of the POS package.

Xbatch

Under X Windows, POS uses the C program Xbatch to draw all its graphics. The function qplot-behavior in qplot-primitives.lisp opens up a text file under usr/tmp. All succeeding drawing commands write out instructions to that file. (e.g. (qplot-line 10 10 100 100) would cause the following line to be written: drawline 10 10 100 100) When all drawing is done, the user calls the function qplot-end-behavior. This function closes the text file and then makes a system call to xbatch with the name of the text file as a parameter. Upon being called, Xbatch parses its input file and displays the specified plots in a newly created window. Thus, the graphics are displayed by a process which is forked by the lisp code in POS. As a result, as long as the machine running qsim supports X Windows, the system call to Xbatch will be the only line of code that has to be changed when porting POS to another Lisp on Unix.

Fonts

All functions in POS will accept font information in the same format as before. (e.g. If you are running on the symbolics, it will take symbolics. If you are on the explorers, it will take explorers fonts. For X Windows, the font keyword can be supplied with a string.) However, the symbolics format for fonts can be used to specify a font on any machine. This font format is specified in the POS manual and will be supported on all platforms in the future.

Colors

You can either specify the alu argument in the old manner where each machine had its own color scheme or you can specify the color as a string. Currently all X Windows colors are supported for POS running under X Windows. However, the code for Symbolics and the Explorers is in the process of being updated. Specifying the color as a string will be supported on all platforms in the future. The variable ps::*colors* is a list of some of the more common colors available.